Flexible substrate, method of fabricating the same, and thin film transistor using the same

Abstract

A flexible substrate for a TFT includes a metal substrate having a predetermined coefficient of thermal expansion, and a buffer layer on the metal substrate, the buffer layer including a silicon oxide or a silicon nitride, wherein the predetermined coefficient of thermal expansion of the metal substrate satisfies an equation as follows,αf+0.162×(1-vf)Ef≤αs≤αf+0.889×(1-vf)EfEf representing Young's modulus of the buffer layer, vf representing Poisson's ratio of the buffer layer, αf representing a coefficient of thermal expansion of the buffer layer, and αs representing the predetermined coefficient of thermal expansion of the metal substrate.

Description

BACKGROUND OF THE INVENTION[0001]1. Field of the Invention[0002]Embodiments of the present invention relate to a flexible substrate, a method of fabricating the same, and a thin film transistor (TFT) using the same. More particularly, embodiments of the present invention relate to a flexible substrate exhibiting reduced deformation during fabrication thereof.[0003]2. Description of the Related Art[0004]Flat panel display devices, e.g., liquid crystal display (LCD) devices, organic light emitting diode (OLED) display devices, and so forth, may include thin and lightweight display panels. For example, since the OLED display devices do not need a back light, the OLED display devices may be implemented in ultra-thin display devices. Flat panel display devices, e.g., OLED display devices, may also exhibit high brightness and a wide viewing angle.[0005]A conventional flat panel display device may include a flexible substrate, e.g., to minimize alignment difficulties and / or damage to the s...

AI Technical Summary

Benefits of technology

[0009]It is therefore a feature of an embodiment of the present invention to provide a flexible substrate capable of preventing or substantially minimizing deformation thereof.

[0010]It is therefore another feature of an embodiment of the present invention to provide a flexible substrate capable of preventing or substantially minimizing delamination of a buffer layer attached thereto.

Problems solved by technology

A conventional flexible substrate formed of plastic, however, cannot be used in a process for forming a TFT of polysilicon or in a high-temperature deposition process for forming an electrode or light emitting diode (LED) on the flexible substrate due to low thermal resistance.

However, since a difference of coefficients of thermal expansion of the metal substrate, i.e., a conductive material, and the buffer layer, i.e., an insulating material, is substantially large, an excessive residual stress may be generated in the buffer layer, thereby deforming, e.g., bending, the metal substrate attached thereto.

Deformation of the metal substrate may cause delamination of the buffer layer from the metal substrate, thereby deteriorating the insulating properties of the buffer layer.